AR-15 Gas System 101

In general, the gas system in the AR-15 enables the weapon to cycle its action. Unlike the gas-piston operation of other semi-auto guns, most the AR-15 utilizes a direct impingement gas system. While they are distant relatives, both systems are distinctly different in operation. It is the direct impingement AR-15 gas system that this text will explore and explain.

Complete AR15 Gas System

The gas system originates in the chamber of the barrel when a round is fired. Expanding gases cause the rounds brass to swell, creating a seal in the chamber, and the bullet begins its trip down the barrel. At some point during this journey, the ever-expanding gases encounter a gas port drilled into the top of the barrel of the gun. This is the point where things really begin to happen.

A portion of the gas is diverted into this port and into the gas block which is attached to the barrel. A metal tube joins the gas block, traveling back to the bolt carrier group and enters via a gas key screwed onto the top of the bolt carrier group. This hot, high-pressure gas causes the bolt to unlock and the residual chamber pressure in the barrel gives the bolt carrier group the inertia needed to begin its trip rearward.

The final, and often overlooked, piece of the AR-15 gas system is the buffer. As the bolt carrier group moves rearward it encounters resistance from the buffer. The weight of the buffer slows the inertia of the bolt carrier group, the buffer spring compresses building the force needed to send the carrier again forward.

From Alpha to Omega, this is the complete AR15 gas system as it exists. This basic direct impingement AR-15 gas system is shared by several other weapons platforms. Its brothers in arms range from the M16, M4, and even its arch nemesis the AR-10. While often maligned, the AR-15 gas system is considered versatile and dependable when properly applied and maintained.

AR-15 Gas System Parts

Gas Block:

You will find four variations of the gas block commonly used in the AR-15 gas system.

Forward Sight Base: The original M16 models issued by the military incorporated the gas block into the forward sight base along with a sling swivel simply for spartan efficiency. A number of shooters who want an old-school, traditional military rifle, bring this style to their AR-15.

Normal height gas block: As the title describes, the gas block is of normal height and will function well. The use of this type of gas block limits your incorporation of a free-floating rail system because it must end at the gas block. Usually, this kind of gas block will have picatinny rail sections on top for front sight attachment.

Low profile gas block: These function in the same manner as the first two, however, its overall dimension gives one the option to install a free-floating rail system.

Adjustable gas block: The complete AR15 gas system relies on the proper amount of gas being available to efficiently perform its job. An adjustable gas block provides a means by which to meter the amount of gas allowed to flow back to the carrier. This is accomplished by adjusting an Allen screw, set into the gas block. Controlling the amount of gas available is one critical step to properly tuning the rifle for specific loads.

Either design of the gas block will accomplish the same task, the choice depends upon the individual shooters tastes and platform requirements. What is critical is the material from which the gas block is constructed. For the most part, most manufacturers won’t offer a gas block made out of aluminum. Although aluminum serves admirably for other components, this is not one of them. The gases present during a firing cycle are very hot and corrosive. Over time aluminum will degrade and ultimately fail in service as a gas block material.

The industry standard material from which to manufacture a gas block is either some form of steel or titanium. These materials are preferred by most shooters due to their durability, ability to withstand heat and their corrosion resistance. There are a number of finishes available to suit individual aesthetics.

Gas Tube:

The sole purpose in life of a gas tube is to transfer the available gas from the gas block back into the carrier via the gas key. Its length will vary depending on the length of a weapons gas system, not necessarily the length of the barrel upon which it serves. Its material does not vary, the industry standard is stainless steel. After all, the gas tube must withstand hot, corrosive gas passing through it for what is hopefully a long time.

If one is firing suppressed or full-auto a great deal of the time some manufacturers offer a black Melonite coating which is non-reflective and is touted to better withstand heat. However, more important than appearance is its alignment. It is critical that the gas block is situated in perfect alignment with the gas key mounted on top of the carrier. Misalignment will cause gas leakage at very least, and destruction of one or more components in the worst case scenarios.

The finish may well be an eclectic choice, although maintenance is not. If you maintain a vigilant watch on cleaning and ensuring proper component attachment, then you have 90 percent of the issue solved. Choosing a reputable manufacturer and dealer is the remainder of the equation. When you look for someone with AR-15 gas systems for sale, you should look at service. Wing Tactical is such a company whose customer service department is knowledgeable and eager to answer any question you may have.

Gas Key:

This is a diminutive element of your AR-15 gas system parts that you shouldn’t take for granted. The only material to consider is either hardened tool steel or titanium. It is mounted atop the carrier and must be able to receive the gas delivered in a harsh and rapidly moving environment. The screws have to be tough, at least Grade 8 and staked in place to ensure that nothing moves.

AR-15 Gas System Lengths

There are four common lengths found in the AR-15 gas system, each has its own unique attributes. Before you look for AR-15 gas systems for sale you must first know the different AR-15 gas system lengths in order to get the correct gas tube.

Pistol Length Gas System: An 5.56/.223 AR-15 barrel that is shorter than 10” will usually uses pistol length gas system. The barrels port is @4” off the back end and the gas tube will be 6.75” long in a pistol length gas system.

Carbine Length Gas System: With a carbine, the barrel will range from 10” to 16” in length. The gas port is @ 7” from the back and the gas tube will be 9.75” long.

Mid-Length Gas System: on a mid-length AR the barrel length will fall between 14” and 20”. Distance to the gas port is @ 9” and the gas tube will be 11.75” long.

Rifle Length Gas System: A gas tube falls into the rifle length gas system category when the gun has a barrel of 20” or longer The gas port will be @ 12.5” in from the back and the gas tube itself is 15.125” long.

Carbine vs Mid-Length Gas System

14.5-inch and 16-inch barrels are the two most common barrel length for AR-15s, and they can be used either carbine or mid-length system. The distance to the gas port ultimately dictates whether you have a carbine length gas system or a mid-length gas system, therefore, which gas tube you have to use. So, you have to measure the distance to the gas port in order to know.

Since the carbine-length gas system has a greater distance between the gas port and the end of the barrel, there will be more gas entering the gas tube. The good thing about this is it will ensure the rifle cycles more reliably, but it will also increase recoil and will cause additional wear on the internals of the weapons.

On the other hand, the mid-length gas system will have less gas entering back to the system, that means less recoil and wear on internal parts. However, if the gas port is undersized, you might run into cycling issues. If you want to have a 14.5-inch barrel with the mid-length gas system, we recommend getting a barrel from a well-known brand to ensure its gas port was drilled properly.

Benefits of Upgrading The Complete AR15 Gas System

When considering AR-15 gas system replacement parts, one should look to function first instead of form. After all, when your gun is assembled most of the parts are even visible. Also, any one of the AR-15 gas system replacement parts has a direct effect on all the others.

If you have the intention of competitive shooting and a wide variety of loads are going to be involved you have no choice but to upgrade your gas system. Even if you are only into self-defense upgrading to more dependable components could be beneficial. Some of the AR-15 replacement gas system parts that should be on your short list are.

Buffer:By varying the buffer and spring weight you can mitigate recoil and muzzle rise, enabling faster and more accurate fire.

Gas Block: A low profile gas block will allow for a longer, free-floating rail to be used. This extends the available surface area for support and accessories.

Adjustable Gas Block: This is crucial if one wishes to finely tune the weapon for a specific load, and limit over-gassing the action. Over-gassing does crudely increase reliability, however, will wreak less havoc on the action of the gun, resulting in longer component life.

If the SHTF: For ultimate action and self-dense use when things cannot fail, upgrade to battle-tested tough. Put in top of the line AR-15 replacement gas system parts, full power ammo, and rock and roll.

AR-15 Aftermarket Gas System Parts

Magazines and the internet are awash with companies offering to sell you the latest gadgets. Certainly, you can get a pretty gas block made from cheap material for a steal. However, your weapon represents a considerable investment in time and money. With that in mind, it’s absolute insanity to risk everything on some cheap junk with no manner of recourse if something goes wrong. Here at Wing Tactical, we have a wide range of aftermarket AR-15 gas system parts made by American owned, reputable manufacturers. Out of personal responsibility, we never offer any AR-15 aftermarket gas system parts that could in any way be misleading, or less than high-quality.

The following is a listing of manufacturers the aftermarket AR-15 gas system parts that we allow to present components for sale on Wing Tactical’s site.

Aero Precision: Based in Tacoma, Washington, their roots are in the aerospace engineering industry. When Aero Precision decided to delve into the firearms industry, they brought that engineering technology and mindset with them. Among their wide range of products, you will find both low-profile gas blocks and Melonite gas tubes. They are well-renowned in the military and law enforcement communities.

Strike Industries: In operation since 2011 and with a US Navy veteran at their helm, Strike Industries is comprised of avid AR-15 and pistol shooters. They are a veteran owned company located in Santa Ana, California designing products with the active shooter in mind. The AR-15 gas system parts they offer up include their enhanced low profile gas blocks and stainless steel gas tubes.

Superlative Arms: Making their home in New Port Richey, Florida, Superlative Arms brings over three decades of Aerospace engineering and manufacturing to the table. Instead of trying to tackle the complete AR15 gas system, they focus on adjustable gas blocks. Their patented design bleeds off the excess gas instead of restricting it, resulting in less carbon fouling in the gas block. Superlative Arms Adjustable Gas Blocks are one of the best on the market. They also offer piston conversion kit in four different gas lengths.

Spike's Tactical: They’re an All American, family-owned company in Apopka, Florida with a dedication to providing every segment of the shooting population with the highest quality parts possible. The AR-15 gas system parts they produce include micro low profile gas blocks as well as gas tubes.

SLR Rifleworks: While producing all of their products in Winter Garden, Florida, the SLR Rifleworks goal is to bring new and innovative products to the firearms market. They are considered to be the pioneers of the Sentry Gas Block which features micro-adjustable, incremented, repeatable settings. Their offerings include both adjustable and non-adjustable gas blocks made from steel and titanium.

Odin Works: Part of Odin Works mission statement is “to make our customers better shooters through the use of our products.” Among other products, the AR-15 gas system parts that Odin Works manufactures are gas tubes as well as low profile and adjustable gas blocks.

Seekins Precision: Seekins Precision is a homegrown, family run company based in Lewiston, Idaho. They have been around for more than a decade engineering answers to problems, not simply making parts. They produce a standard adjustable gas block as well as their Select Adjustable model. The new select version adjusts from the front without tools, making it much more user-friendly in the field.

The Choice Is Easy After You Have All The Information

Unless you only shoot a box or two of ammo a year there are significant reasons to consider upgrading your AR-15 gas system. It is a wide stretch from good enough all the way to premium. If you are content plinking at the occasional can in the backyard then good enough, is good enough in your world. If you swing to the far end of the spectrum and are an Olympic class shooter who dedicates hours of time daily to your craft, then the premium level is where you're at.

Granted, the majority of shooters fall safely in the middle, and the judicial application of the proper equipment can make your shooting more rewarding. Personally, I question my own abilities after every shot. If only in the back of my mind, the thought of whether more practice or better equipment would have made a difference. Realistically speaking, everyone has their natural limitations which no amount of training or equipment can overcome. With that being said, all of us can become better.

The first matter to address is are you going to require a complete AR15 gas system or just a piece or two? The answer to that conundrum will only come by knowing what you now have installed on your weapon and to what end purpose you want to achieve.

Are the fasteners in the gas key properly staked? Perhaps you want to shake up the variety of ammo you use and get more into competitive matches. Is the main purpose of your AR-15 going to be home defense? Take a look at all of your AR-15 gas system parts. Do any of them appear to be stressed, cracked, or failing?

Another point of consideration is the overall length of your weapon. 50+ years ago when the old M16 popped up in Vietnam there weren’t many choices. In today's world, the options are vast. The burn rate of gunpowder has greatly improved, as has bullet selection. You can mix-and-match barrel lengths with the AR-15 gas system lengths to custom fit the weapon’s overall length, with your shooting style and demands.

Regardless of your goals or budget, you are in the right place to make it happen. Wing Tactical is proud to offer a wide selection of quality AR-15 gas system replacement parts. If you have any question as to which direction you should go please do not hesitate to send us an e-mail. We look forward to helping you reach your goals, both now and in the future.